1. Field of the Invention
The present invention concerns a magnetic resistance effect type magnetic head which is installed in hard disk drives, etc., and a method for manufacturing the same. More specifically, the present invention concerns a spin-valve magnetic head which has a high output, low noise and stable output characteristics useful for high-density recording.
2. Background Information
As surface recording density has increased in recent years, composite heads in which a magnetic resistance effect type head equipped with a magnetic resistance effect element (MR element) as a magnetism-sensing part is integrally laminated with an inductive head used for recording have become the mainstream of thin-film magnetic heads installed in hard disk drives.
The term xe2x80x9cmagnetic resistance effectxe2x80x9d refers to an effect in which the electrical resistance changes when a magnetic field is applied to a conductive magnetic material. Variations in magnetic fields can be detected utilizing an element which has this effect, so that information recorded on a magnetic medium can be read. Such magnetic resistance effect elements include anisotropic magnetic resistance effect elements (AMR elements) which are equipped with a ferromagnetic thin film that has uniaxial anisotropy in the direction of the sensing current, and in which the electrical resistance of this ferromagnetic thin film varies as a result of rotation of the magnetization when an external magnetic field is applied from a magnetic recording medium in the direction of the axis of difficult magnetization, and GMR elements such as spin-valve elements which show a large magnetic resistance effect, etc. In the case of the magnetic resistance effect type elements, a sensing current is applied and the variation in resistance is detected; i.e., the magnetic field is detected rather than a time differentiation of the magnetic flux. Accordingly, the output is unaffected by the movement speed of the magnetic recording medium, so that there are essentially no frequency limits in practical bandwidths. Consequently, there is no inherent noise mechanism that causes deterioration of the signal-to-noise ratio. Furthermore, size reduction is easy, and information recorded on a magnetic recording medium at an extremely high surface recording density can easily be distinguished and extracted.
In such magnetic resistance effect heads, a magnetic resistance effect element is ordinarily disposed between upper and lower shielding layers with gap layers interposed, and a pair of electrode layers (left and right electrode layers) which apply the sensing current to the element are connected to both end portions of the element. Furthermore, in order to form the magnetic resistance effect element into a single magnetic domain and eliminate the generation of Barkhausen noise, hard bias layers are disposed on both edges of the element. In the case of current spin-valve heads, the electrodes used to apply current to the spin-valve film usually employ an abutted junction structure adjacent to the end portions of the spin-valve film (for example, see Japanese Patent Application Kokai No. 10-154314).
There has been a demand from the industry to increase the memory capacity of hard disk drives at the rate of 60% per year. As a result of this demand, it has been necessary to achieve a much greater increase in recording density. In order to increase the recording density, improvement of the operating characteristics of both the inductive head and the magnetic resistance effect head is an essential technical task. The main technical tasks in magnetic resistance effect heads are improving durability with respect to electrostatic discharge, increasing the output, narrowing the track width and handling a narrow gap width.
In recent years, as a result of the employment of lead overlaid structures in which the electrodes are overlapped on the upper portion of the MR element of a spin-valve film, etc., the durability of heads with respect to electrostatic discharge has been improved, and it has been possible to narrow the track width of the playback head without lowering the sensitivity. Furthermore, it has been reported that noise and hysteresis are also controlled (for example, see Japanese Patent Application Kokai No. 9-282618, Nikkei Electronics 1998, 11, 2, p.54, etc.).
One embodiment of the present invention obtains a thin-film magnetic head in which the sensitivity distribution of the spin-valve element is good, and which has a large output and little noise or hysteresis. In one embodiment, a spin-valve head includes a spin-valve element and a pair of electrode layers that are electrically connected to both ends of this element in the direction of width. In one embodiment, a tantalum film is laminated as a protective layer on the uppermost part of the element, and the pair of electrode layers are caused to overlap on both end portions of the element. In one embodiment, the tantalum oxide present in the areas on which the electrode layers overlap is removed prior to the formation of the electrode layers so that the electrical resistance between the electrode layers and the element is reduced.